1. Field of the Invention
This invention relates generally to transducer suspension systems and more particularly to a suspension system with stacked electrical leads.
2. Description of the Prior Art
Direct access storage devices (DASD), or disk drives, store information on concentric tracks of a rotatable magnetic recording disk. A magnetic head or transducer element is moved from track to track to record and read the desired information. Typically, the magnetic head is positioned on a air bearing slider which flies above the surface of the disk as the disk rotates. In some recently proposed disk drives, the slider (or carrier) rides on a liquid film or bearing on the disk. A suspension assembly connects the slider to a rotary or linear actuator. The suspension provides support for the slider.
Examples of suspension systems are shown in the following references: U.S. Pat. No. 5,560,097, issued Oct. 1, 1996, by Bajhorek et al; U.S. Pat. No. 5,519,552, issued May 21, 1996, by Kohira et al; U.S. Pat. No. 5,491,597, issued Feb. 13, 1996, by Bennin et al; U.S. Pat. No. 4,996,623, issued Feb. 26, 1991, by Erpelding et al; U.S. Pat. No. 4,975,795, issued Dec. 4, 1990, by Spash; U.S. Pat. No. 4,819,094, issued Apr. 4, 1989 by Oberg; U.S. Pat. No. 4,645,280, issued Feb. 24, 1987, by Gordon et al; U.S. Pat. No. 3,960,622, issued Jun. 1, 1976 by Hofling et al; U.S. Pat. No. 3,633,189, issued Jan. 4, 1972 by Billawala; U.S. Pat. No. 3,269,861, issued Aug. 30, 1966, to Schneble et al; U.S. Pat. No. 3,051,954, issued Aug. 28, 1962, by Osterlund; TW 276333, published May 21, 1996, by Klaasen; Japanese Patent Application 06-194945, published Feb. 16, 1996, by Matsumoto et al; Japanese Patent Application 05-81630, published Oct. 21, 1994, by Yamamura et al; Japanese Patent Application 03-211668, published Jun. 22, 1993, by Inaba; Japanese Patent Application 55-93422, published May 22, 1982, by Watanabe; Japanese Patent Application 51-104787, published Mar. 22, 1978, by Takahashi; and Japanese Patent Application 4-272635, published May 6, 1994.
The suspension must meet several requirements. The suspension must be flexible and provide a bias force in the vertical direction. This is necessary to provide a compensating force to the lifting force of the air bearing in order to keep the slider at the correct height above the disk. Also, vertical flexibility is needed to allow the slider to be loaded and unloaded away from the disk. Another requirement of the suspension is that it must provide a pivotal connection for the slider. Irregularities in operation may result in misalignment of the slider. The slider is able to compensate for these problems by pitching and/or rolling slightly to maintain the proper orientation necessary for the air bearing. Another requirement of the suspension is that it must be rigid in the lateral direction. This is needed to prevent the head from moving from side to side, which would result in the head reading the wrong track.
Disk drives have become smaller in size and their recording track density has increased dramatically. This has necessitated the use of smaller and smaller heads and suspensions. The smaller size makes it more difficult to string individual wires along the suspension to the head. Recently, it has been proposed that electrical leads be etched directly into the suspension in order to do away with the need to string separate wires.
However, these etched leads may have some disadvantages. The separately strung wires of the past were strung in twisted wire pairs. These twisted pairs were effective in canceling out the effects of external noise. The new etched leads run parallel to one another along the surface of the suspension and do not achieve the same degree of noise cancellation.
Another disadvantage of the etched leads is that they require a certain distance of spacing between them. In the smaller suspensions of the future, the suspension width may limit the number of electrical leads. The newer transducer heads may require more electrical leads than in the past. What is needed is a suspension system which solves these problems.